Lubricating grease compositions containing acyl derivatives of dihydroxy diamino anthracene



United States- Patent Officef wnmcnrmo GREASE COMPOSITIONS CON- I TAINING ACYL. DERIVATIVES F DIHY- DROXY DIAMINO ANTHRACENE Delmer L. Cottle, Highland Park, David w. Young, Westfield, and Arnold I. Morway, Clark, N. 1., assignors to Esso Research and Engineering Company, a corporatlon of Delaware No Drawing. Appllcatlonlnly 28, 1954, Serial No. 446,414

9 Claims. (CL 252-405) This invention relates to lubricating grease compositions. Particularly, the invention relates to lubricating greases which have outstanding resistance to oxidation and whichhave good structural stability obtained with minor amounts of soaps. More particularly, the invention relates to improved lubricating greases which comprise a lubricating oilbase stock containing combined therewith a minor amount of defivative of 9,10-dihydroxy-l,4-diamino-anthracene.

Lubrication engineers have long recognized the need for a lubricating grease composition which does not contain ash-forming soaps, or at least, for greases in which the ash-forming soap component is at a minimum.- There are many industrial uses for greases which will not leave deposited upon bearing surfaces the highly corrosive and friction increasing soap residues when the oil component has become volatilized.

Methods of increasing the resistance to oxidation of a grease composition is also a problem that has held the attention of lubricant experts for some time. Generally this has beendone by incorporation into the composition substances known to the art as oxidation inhibitors. There are various of these oxidation inhibitors known to the art, examples being such materials as phenyl-alphanaphthylamine, phenyl beta naphthylamine, phenolic compounds, complex amine intermediates and the like.

It has now been found, and forms the object of this invention, that derivatives of 9,10-dihydroxy-l,4-diaminoanthracene perform a double function when incorporated into lubricating oils in various proportions. Certain of these derivatives operate as both oxidation inhibitors and as soap substitutes or thickening agents for the lubricating oil.

The materials of the instant invention may be grouped under the following generic formula:

on NH-ii-R may be 'used as a catalyst for the reaction. The product may be purified by slurrying with water containing small amounts of caustic.

When it is desired to utilize the compounds of the instant invention to prepare lubricating greases thatcontain no ash-forming soaps, from about 0.5 to about 10.0

wt. percent, preferably from about 1.5 to about 5.0 wt. percent of the acyl dihydroxy diamino anthracene is incorporated into a lubricating oil. When it is desired to enhance the oxidation resistance of a lubricating grease composition, from about 0.5 to about 2.0 wt. percent of the compound is used.

The acyl derivatives of the dihydroxy diamino anthracene are readily soluble in lubricating oils and the compositions are prepared quite simply by raising the temperature of the physical mixture to the melting point of the compound and allowing the solution to cool.

As was stated above, the grease compositions of this invention comprise a lubricating oil base stock containing combined therein a minor amount of an acyl derivative of a dihydroxy diamino anthracene. The greases ofinvention may or may not contain other thickening agents and other additive materials, suchas other antioxidants and the like.

The lubricating oil chosen to form the greases of invention may be widely varied. The oil chosen to prepare the grease composition should be capable of performing the lubricating function if it could be used as a liquid. Mineral lubricating oils having a viscosity within the range of from about 35 to about 200 SUS' at 210 F. may be used for most applications. The mineral oil may be of a parafiinic or of a naphthenic nature depending upon the crude source, and any of the various distillates refined by the various refinery techniques are operable.

Synthetic lubricating oils may also .be utilized in preparing the lubricating greases of this invention. Synthetic lubricating oils having a viscosity within the range stated above are operable. These oils include esters of mono-basic acids, ,such as the C OX0 alcohol ester of C Oxo acid, esters of C Oxo alcohol and octanoic acid, etc., esters of dibasic acids, such as di-Z-ethylhexyl sebacate,,di-nonyl adipate, etc., esters of glycols, e. g. the C 'oxo acid diester of tetraethylene glycol, etc., complex esters such as the complex ester formed byreacting esters formed by reacting one mol of tetraethylene glycol In the formula, R represents an alkyl group containing 0 from about 3 to 24 carbon'atoms.

Although the acyl derivatives of the 9,10-dihydroxy- 1,4-diamino anthracene within the range set out above have both oxidation inhibiting properties and thickening power when it is desired to use the materials of inwith two mols of sebacic acid and two mols of 2-ethyl hexanol, complex esters formed by reacting together one mol of azelaic acid, one mol of tetraethylene glycol, one mol of C 0x0 alcohol, and one mol of C Oxo acid, and the like, esters of phosphoric acid, such as the ester formed by contacting three mols of the mono-methyl ether of ethylene glycol with one mol of phosphorus oxychloride, halocarbon oils, such as the polymers of chlorotrifluourethylene, alkyl silicon compounds, such as methyl polysiloxanes, ethyl polysiloxanes, methyl-phenyl polysiloxanes, ethyl-phenyl polysiloxanes and the like, sulfite esters such as those formed by reacting one mol of sulfur oxychloride with 'two mols of the methyl ether of ethylene glycol and the like, carbonates such as those formed by reacting C Oxo alcohol with ethyl carbonate to form a half ester and reacting this half ester with tetraethylene. glycol, mercaptals such as those formed by reacting 2-ethylhexyl mercaptan with formaldehyde, formals such as those formed by reacting C 0x0 alcohol with formaldehyde, polyglycols, such as those formed by condensing butyl alcohol with up to fifty units of propylene oxide, or mixtures of any of the above synthetic oils in any proportions.

When it is desired to utilize a minor amount of the commonly known grease-forming soaps in formulating 2,816,074 I Patented Dec. 10, 1957 soaps of fatty acids such as the sodium, potassium, lithium,

barium; calcium, strontium soaps of such acids as hydrogenated fish oil acids, stearic acid, hydroxy-stearic acid, oleic acid,palmitic acid, lauric acid, tallow, coconut oil acids, and the like. The saturated or unsaturated glycerides of the various fatty acids may be used as may mixtures of any of the soaps mentioned above. Complex soaps may also be used, such as those prepared from mixtures of the high molecular weight fatty acids-and low molecular weight acids such as acetic, furoie and the like. When an ashless thickener is desired, polyethylene resin may be employed in combination with the acyl derivative and this combination may in turn be employed with n inor amounts of simple or complex soap thickeners.

Among the various additive materials which may be incorporated into the grease compositions of invention may be mentioned tackiness agents, such as polyolefinic materials, other antioxidants, such as phenyl alpha naphthylamine, coloring agents, extreme pressure inhibitors and the like.

Very desirable high temperature grease compositions have been prepared in the past by using as a thickening agent a mixture of a metal salt, such as the calcium salt of a low molecular weight fatty acid such as acetic acid and a metal soap of a high molecular weight fatty acid, such as calcium stcarate, 'etc., the ratio of said salt to said soap being from 1:1 to 20:1, preferably 7.5:1 to 10:1. These excellent high temperature greasecompositions tend to harden excessively on storage. There first appears on the surface of these greases a hard crust which gradually extends throughout the body of the grease. It has been proposed to eliminate this crust formation and hardening eifect by the incorporation of minor amounts of hydroxy fatty acids such as the monoor di-hydroxy stearic acids, hydrogenated castor oil and the like. Another desirable characteristic of the anthracene derivatives listed above, however, is that these materials tend to eliminate this hardening and crusting effect of these complex salt-soap high temperature greases. This elimination of hardening is shown by data given below.

Another desirable aspect of the incorporation of the acyl derivatives of the dihydroxy diamino anthracenes is the fact that a very desirable color is imparted tothe grease composition. Since these materials are related to alizarin, they are dyes and impart a royal purple color to the grease. The grease does not stain the hands or clothing and the dark color. gives an easily discernible thin film on operative bearings, an advantage which will be readily apparent to those skilled in the art.

The invention will be more clearly demonstrated by the following illustrative examples.

, EXAMPLE I Formulation Ingredients Preparation Charged oil, hydrated lime and the acid to a fire heated kettle and while stirring warmed to 135 F. Then added the acetic acid and continued heating to 500 F. Shut oil heat and cooled to 300 F. when the N- stearoyl dihydro di-amino anthraquinone was added. Continued cooling to 250 P. where a sample was taken 4 for oxidation testing. To the balance was added the phenyl alpha naphthylamine and the grease further cooled to 200 F., homogenized, filtered and packaged.

Properties Appearanee. Excellent, smooth, homogeneous dark 1: le roduct. Penetrations 77 1'. mm./10 D ID p Unworked. 808A f ter 8 mos. storage Worked strokes -345 L'ter 8 mos. storage Worked 100,000 strokes-.. sea. Dropping point, one. Whee hearing test (6 hrs. at

220' ll Pass, no leakage.

Norma nail-minimum" Phen l anap No added Inhib.

' Present Hours to 5 p. s. 1. drop in pressure 1 Hours to 10 p. s. 1. drop in pressure Phase changes None on heating to 450' I. (No tendency 0 thin out or become excessively hard or rubbery.) Lubrication life hours (10,000 R. P. 11-250 1'.) 1389.

l A grease composition oi a similar formulation but without the anthraoeggod ari vgtive hardened on 3 months storage from a penetration value 0 greasecompositlon oi a similar formulation but without the anthraottiggodgilvssbtive hardened on 3 months storage from a penetration value 0 A straight soap thickened grease with no inhibitor present gives an oxidation life in this test of 5 p. s. 1. drop in oxygen pressure in 10 hours.

EXAMPLE Il Formulation Ingredients Percent Weight N -stearoyl diamino dihzdroxy anthraquinone 6. 0 Mineral oil (56 BUS/210 F.) 95. 0

Preparation 2 The oil and N-stearoyl diamino dihydroxy anthraquinone were mixed together and heated to 300 F. The

mixture was then cooled rapidly in thin layers. An excellent smooth buttery grease was obtained.

Properties Appearance Excellent, smooth, rich p u r p l e grease.

Penetrations 77' F. mm./ 10:

Unworked 300.

Worked 60 strokes 310. Dropping point. 235 F.

Norma Hoifman oxidations:

Hours to 5 p.'s. i. pressure drop 235.

Charged N-stearoyl diamino dihydroxy anthraquinone, polyethylene resin and di-Z-ethyl hexyl sebacate to a fire heated kettle and warmed to 350 F. Held at this temperature until the polyethylene resin was completely dispersed in the ester. Then poured in pan for cooling in shallow layers.

Properties Appearance Excellent, smooth purple grease. Penetrations 77 F. mm./:

Unworked 28S. Worked 60 strokes 310.

Norma Hofiman oxidations:

Hours to 5 p. s. i. drop in pressure 185. Low temperature performance- Time for 1 complete revolution of a 204 bearing 7.0 seconds.

To summarize briefly, this invention relates to improved lubricating grease compositions which are prepared by incorporating into a lubricating oil a minor amount of a material of the formula OH NH! o H mac-n wherein R is an alkyl group containing from about 3 to about 24 carbon atoms. The materials are termed acyl derivatives of 9,10-dihydroxy-1,4-diamino-anthracene. When R contains from about 3 to about 16 carbon atoms, the optimum oxidation inhibition is obtained and when R is from 12 to about 22 carbon atoms in length, maximum thickening etfect is noted. The acyl derivative is incorporated into the lubricant in amounts varying from about 0.5 to about 8.0% by weight, based on the weight of the total composition. One very desirable lubricating grease composition is prepared by thickening a lubricating oil, either a naturally occurring mineral oil, or a synthetic oil, with a combination of a metal salt of a low molecular weight fatty acid, a metal soap of a high molecular weight fatty acid and with from 2.0 to 8.0 wt. percent of the acyl derivative containing from about 8 to about 18 carbon atoms in the acyl group, and combining therewith from about 0.1 to about 1.0 wt. percent of phenyl alpha naphthylamine. In this combination, the acyl derivative enhances the thickening etfect'of the soap thickener and the oxidation resisting eflect of the phenyl-alpha-naphthylamine.

We claim:

1. A lubricating grease composition which comprises a lubricating oil base stock containing combined therein hem about 0.5 to about 10.0 wt. percent of a material of the Eula wherein R is an alkyl group containing from about 3 to about 20 carbon atoms.

2. A lubricating grease composition which comprises a iubrica oil base stock containing combined therein from about 0.5 to about 2.0 wt. percent of a material of the formula OH NH:

H NE

c=o R wherein R is an alkyl group containing from 10 to 24 carbon atoms.

4. A lubricating grease composition which comprises a lubricating oil base stock thickened to a grease consistency with a material of the formula on NE,

wherein R is an alkyl group containing from 3 to 24 carbon atoms.

5. A lubricating grease composition according to claim 4 wherein R is an alkyl group containing from 10 to 24 carbon atoms. 1

6. A lubricating grease composition according to claim 4 wherein R is an alkyl group containing 18 carbon atoms.

7. A lubricating grease composition which comprises a lubricating oil base stock thickened to a grease consistency with a mixture of a salt of a low molecular weight fatty acid and a soap of a high molecular weight fatty acid, the ratio of said salt to said soap being within the range of from about 7:5 to 10: 1, said grease composition containing combined therein a minor, but oxidation resisting, amount of a material of the formula No references cited. 

